104 SCIENCE PROGRESS. 



the present position of the doctrine, we have seen that the 

 result of the vast amount of research which has been carried 

 on since it was first promulgated, has but served to establish 

 it upon a broader and sounder basis. Moreover it has been 

 pointed out that the concept of a material metamor- 

 phosis — that is of a genetic relation between the different 

 forms of the same member — is the one which has the weight 

 of evidence in its favour ; though opinions are still divided, 

 in the case of the leaf, as to whether the primitive form 

 was a sporophyll or a foliage-leaf. In using the expression 

 " material metamorphosis," it is not implied that every 

 metamorphosed organ once actually possessed the form of 

 its primitive member, assuming it as a necessary phase in 

 its development ; on the contrary, the idea involved is that, 

 whilst all the embryonic organ-rudiments are potentially 

 capable of developing into their appropriate primitive form, 

 many of them do actually develop, under normal condi- 

 tions, more or less directly into secondary, metamorphosed 

 forms. It will also have been gathered that metamorphosis 

 has a deep physiological significance, inasmuch as it is by 

 this means that the few primitive members of the plant be- 

 come multifariously adapted as organs for the performance 

 of a great variety of functions ; and herein the leaf is pro- 

 minent as the most plastic member of the body. In fact, 

 a higher degree of metamorphosis is the external expression 

 of a more complete division of physiological labour. 



But if the store of knowledge on the subject has amaz- 

 ingly increased since the time of Wolff and of Goethe, it 

 is still far from complete. This is a confession which has 

 always to be made when stock is taken of what is known 

 on any scientific subject ; for in no branch of Science is 

 finality even in sight, and it is doubtless this that lends 

 charm to the pursuit. In this subject we have still to dis- 

 cover the mysterious law of which Goethe speaks in the 

 lines : — 



Alle Gestalten sind ahnlich und keine gleichet der andern ; 

 Und so deutet das Chor auf ein geheimes Gesetz, 

 Auf ein heiliges Rathsel. 



S. H. Vines. 



